The Process and Precautions

The number of supernovae discovered in recent years has increased dramatically due to the availability of better hardware and applications. For this reason I have recently moved the checking of the Central Bureau's (CBAT's) "Recent Supernova" Web page to the top of the list. I check this, even though I subscribe to the IAU circulars alerting me to the latest discoveries. The circulars get to me quicker and give more details, but the CBAT page is a backup in case I miss any. The process is as follows:

1. Check CBAT's Recent Supernova page for already-discovered supernovae. Go back at least 12 months when checking. I check the whole list. That's why it's there. Check not only by galaxy name but also by its coordinates.

2. Check the Minor Planet Center page for known asteroids, at that location, at that time. This should be done for both the discovery image and the confirmation image.

3. Check past patrols. I NEVER throw images away. All of the patrols I have ever made are saved on CDROMs and archived. These are an invaluable resource when checking for possible variables, especially dwarf novae, in the field.

4. At this point I will stop one of the telescopes and go for at least one confirmation image. I try for multiple images, usually ten, if the weather allows. This process eliminates hot pixels and cosmic ray hits, which can cause starlike artifacts to appear.

5. I do astrometry on the suspect, on the discovery image and on the last confirmation image. If there is a difference of greater than one arc-second, I will wait and re-image as late as possible that night. This might be due to the suspect being an as yet uncharted asteroid.

6. I have recently added an additional check. I have created a list of "falsely reported" supernovae by others from the CBAT archive. This alerts me to fields where dwarf novae, variable stars and even HII regions have caused problems in the past. If the coordinates match even roughly, I become suspicious.

7. If all these things check out, I measure the offsets (the number of arc-seconds, e.g., north or south of the galactic nucleus) of where the suspect lies. I then prepare a preliminary report for CBAT.

8. A supernova has to be imaged and its position measured over at least two "periods of darkness" to ensure that it is not a moving object. This is usually over two nights but if the weather is likely to be a problem I will contact colleagues abroad, perhaps in the United States or Japan, and request that they take a confirmatory image. In these cases, the images might be less than a day apart but would still be acceptable if the astrometry showed no perceptible movement.

If all of these prove positive I will prepare a final report and draft release for the Central Bureau. Please see the following samples.

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